1. Field of the Invention
This invention relates to a bone assessment apparatus and bone assessing method and more particularly to an apparatus and method for measuring physical parameters of a test part of a patient and computing data useful in diagnosing bone disorders by using measuring waves, such as an X-ray and an ultrasonic wave, transmitted and received through the test part.
2. Description of the Related Art
A bone assessment apparatus is disclosed in U.S. patent application Ser. No. 08/063,779 which can provide information useful for diagnosis of bone disorders through X-ray measurement or ultrasonic wave measurement. More specifically, physical parameters of a calcaneus or heel bone (hereinafter referred to as a test part), i.e. a bone mineral density calculated from an attenuation coefficient of an X-ray, and an ultrasonic wave propagation velocity, are obtained to compute a bone assessment index in order to determine whether or not the subject suffers from a bone disorder.
It is well known that, in transmitting and receiving an ultrasonic wave through a test part, an air layer existing between the ultrasonic transducers and the test part attenuates and reflects the ultrasonic waves, which degrades a measuring accuracy. For this reason, it has been performed to eliminate the air layer by filling the space between the transmitting/receiving devices and the test part with an acoustic matching material. Similarly, since X-rays are also attenuated if an air layer exists between the X-ray generator/detector and the test part, the air layer should be eliminated for keeping a measurement of precise bone mineral density. Thus, it has also been desired to provide a material equivalent to soft tissue such as skin or muscle between the test part and the transmitting/receiving devices.
In order to avoid the adverse affects of the air layer, a conventional apparatus has employed a bath containing water (preferably, distilled water containing a surface active agent) which functions both as a matching material for acoustic wave measurement and a soft tissue equivalent material for X-ray measurement. Then, the test part is immersed in the water, and ultrasonic waves and X-rays are irradiated through the water to the test part for measuring each of the physical parameters.
However, when a number of measurements are repeated by the conventional apparatus for many different patients, for example, at a mass checkup where only a primary diagnosis is made simply for deciding if the patient is suffered any bone disorder or not (this is called screening), many test parts are directly immersed in the coupling water in the bath, which quickly causes contamination of the water. Changing water at each time whenever a patient subject changes is not efficient.